Dissociative multiple ionization following valence, Br(3d), and Si(2p) inner shell photoexcitation of SiBr₄ in the range of 30-133 eV

The photoionization of SiBr₄ in the valence shell, and the Br(3d) and Si(2p) inner shell excitation/ionization regions, has been studied by using a time-of-flight mass spectrometer and synchrotron radiation over the range 30-133 eV. The photoionization efficiency curve of SiBr₄ has been recorded as a function of the incident photon energy. Dissociation processes of SiBr₄ have also been investigated by photoelectron-photoion coincidence and photoion-photoion coincidence (PIPICO) techniques. Various monocations of Br_n⁺ (n = 1,2) and SiBr_n⁺ (n = 0-4) are detected along with dications of Br²⁺ and SiBr_n²⁺ (n = 0, 1, 3) in the energy range. Various dissociation patterns are proposed based on the measurements of the ion time-of-flight differences in the PIPICO mode. The dominant dissociation pattern is found to be Si⁺-Br⁺ and SiBr⁺-Br⁺ in the whole energy examined. In the Br(3d) excitation region, however, a fragmentation leading to ion pair such as SiBr₃⁺-Br⁺ also plays an important role in the dissociation of the core-excited SiBr₄. With the help of ab initio Hartree-Fock and previous CI calculations, we estimate the term values and symmetries of the discrete core-excited states. This study of the specific excitation and dissociation of molecules provides information on energy dissipation processes of the core-excited states.